This invention relates to a stereospecific process for producing azetidinones which are useful as intermediates for preparing penems and carbapenems. More particularly, this invention relates to stereospecific processes for producing an azetidinone represented by the formula ##STR2## wherein R"" is hydrogen, halogen or lower alkyl, from L-threonine by converting the L-threonine to an epoxyamide then to the azetidinone. The azetidinone is converted to penems and carbapenems by a series of steps, all of which are known in the art.
The process of this invention provides a means for production of azetidinones of specific stereochemistry which are intermediates for stereodefined penems and carbapenems by utilizing readily available, inexpensive starting materials.
Hanessian, et al., J.A.C.S. 107, 1438-9 (March 1985) discloses a process of making azetidinones from L-threonine via an epoxyamide. The process is similar but not identical to the invention described herein.
Yanagisawa, et al., Tetrahedron Letters 24, 1037 (1983) disclose a process for making phenylsulfonylazetidinones from L-threonine, via an epoxyamide.
Shiozaki, et al., Heterocycles, 22, 1725 (1984) disclose preparation of cyanoazetidinones from 2,3-epoxybutyric acid, an intermediate in the process of this invention.
Shiozaki, et al., Tetrahedron, 40, 1795 (1984) disclose a process of transforming L-threonine stereospecifically to an azetidinone used for making the carbapenem thienamycin.